Abstract : The tooth-tissue supported RPD (distal extension base) must depend on two completely different type more

Abstract : The tooth-tissue supported RPD (distal extension base) must depend on two completely different types of support—the relatively immobile teeth, and the displaceable tissues of the edentulous ridge. It has been reported that tissue resiliency is four to twenty times the axial displaceability of abutment tooth, with the muco-periosteum exhibiting eight times the thickness of periodontal ligament. These differences in the support mechanics of the distal extension base creates the potential for the prosthesis to rotate around a fulcrum line established through the most terminal rests seats of the RPD framework assembly. Uncontrolled rotations around a fulcrum line are known to be highly detrimental to the RPD abutment teeth through off-axis or non-vertical loading forces. Measures must be taken in the design and fabrication of a tooth-tissue supported RPD to absolutely minimize tissue-ward movement of the prosthetic distal extension base under functional loading. The article will describe a secondary impression method which utilizes the metal RPD framework to hold custom impression trays to: a) record the edentulous areas in a functionally displaced position so as to help the RPD resist tissue-ward movement around the primary fulcrum line and b) obtain soft tissue support to aid abutments in resisting functional stresses. This is accomplished by selective tissue displacement. - Slides less